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// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package packet
import (
"crypto/openpgp/error"
"crypto/rand"
"crypto/rsa"
"encoding/binary"
"io"
"os"
"strconv"
)
// EncryptedKey represents a public-key encrypted session key. See RFC 4880,
// section 5.1.
type EncryptedKey struct {
KeyId uint64
Algo PublicKeyAlgorithm
Encrypted []byte
CipherFunc CipherFunction // only valid after a successful Decrypt
Key []byte // only valid after a successful Decrypt
}
func (e *EncryptedKey) parse(r io.Reader) (err os.Error) {
var buf [10]byte
_, err = readFull(r, buf[:])
if err != nil {
return
}
if buf[0] != 3 {
return error.UnsupportedError("unknown EncryptedKey version " + strconv.Itoa(int(buf[0])))
}
e.KeyId = binary.BigEndian.Uint64(buf[1:9])
e.Algo = PublicKeyAlgorithm(buf[9])
if e.Algo == PubKeyAlgoRSA || e.Algo == PubKeyAlgoRSAEncryptOnly {
e.Encrypted, _, err = readMPI(r)
}
_, err = consumeAll(r)
return
}
// DecryptRSA decrypts an RSA encrypted session key with the given private key.
func (e *EncryptedKey) DecryptRSA(priv *rsa.PrivateKey) (err os.Error) {
if e.Algo != PubKeyAlgoRSA && e.Algo != PubKeyAlgoRSAEncryptOnly {
return error.InvalidArgumentError("EncryptedKey not RSA encrypted")
}
b, err := rsa.DecryptPKCS1v15(rand.Reader, priv, e.Encrypted)
if err != nil {
return
}
e.CipherFunc = CipherFunction(b[0])
e.Key = b[1 : len(b)-2]
expectedChecksum := uint16(b[len(b)-2])<<8 | uint16(b[len(b)-1])
var checksum uint16
for _, v := range e.Key {
checksum += uint16(v)
}
if checksum != expectedChecksum {
return error.StructuralError("EncryptedKey checksum incorrect")
}
return
}
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